The human eye's sensation of a color picture varies in accordance with the color temperature of the color picture displayed on the screen of the video appliance such as a television receiver. For instance, the blue color group which gives the cool feeling to the viewer has a low color temperature, and the red color group which gives the warm feeling to the viewer has a high color temperature. The color temperature as described above is one of important color control parameters for providing an optimum picture to the viewer eye's sensation.
There is disclosed an automatic color control device for a television receiver which senses the brightness and color of the exterior environment of the television receiver and determines the optimum picture display condition whereby a viewer does not feel eye strain in accordance with the sensed brightness and color of the environment.
The conventional color control device for a television receiver, as shown in FIG. 1, includes a chromaticity sensing section 11 for sensing the environmental brightness and the environmental color of the television receiver, converting the sensed signals into corresponding voltage values, and amplifying the voltage values, a microprocessor 12 for recognizing the current information on the environmental brightness and color in accordance with the voltages outputted from the chromaticity sensing section 11 and outputting control signals in response to the recognized information, and a video processor 10 for controlling the brightness and color of a displayed picture in accordance with the control signals outputted from the microprocessor 12 to provide the picture optimum to the viewer eye's sensation.
The video processor 10 comprises a decoder and digital-to-analog (D/A) converter 13 for outputting a contrast control signal, brightness control signal, and color control signal in accordance with the control signals from the microprocessor 12, a contrast control section 14 for controlling the amplitude of input primary color signals of R(red), G(green), B(blue) in accordance with the contrast control signal outputted from the decoder 13, a brightness control section 15 for controlling the brightness of the picture by controlling the DC bias voltage of the RGB primary color signals amplitude-controlled by the contrast control section 14 in accordance with the brightness control signal outputted from the decoder 13, a white point control section 16 for properly controlling respective levels of the RGB primary color signals outputted from the brightness control section 15 in accordance with the color control signal outputted from the decoder 13, and an output buffer section 17 for buffering the RGB primary color signals outputted through the white point control section 16 to output the buffered primary color signals to a cathode ray tube (CRT) driving circuit (not illustrated).
The operation of the conventional color control device as constructed above will now be explained.
A luminance sensor Cy in the chromaticity sensing section 11 senses the brightness of the environment of the television receiver, and a color sensor Ye senses the color of the environment.
At this time, the resistance of the luminance sensor Cy varies in proportion to the environmental brightness, and the resistance of the color sensor Ye varies in proportion to the environmental color. For instance, if the environmental color contains an intensified blue color, the resistance of the color sensor Ye is lowered, while the environmental color contains an intensified red color, the resistance of the color sensor Ye is heightened.
The output voltages, i.e., the sensed signals of the luminance sensor Cy and the color sensor Ye are inputted to non-inverting terminals (+) of operational amplifiers OP1 and OP2, and reference voltages are inputted to inverting terminals (-) thereof, respectively.
The operational amplifiers OP1 and OP2 amplify the differences between the sensed signals and the reference voltages, respectively, and provide their outputs to the microprocessor 12.
The microprocessor 12 recognizes the information on the environmental brightness and color of the appliance according to the output voltage values of the chromaticity sensing section 11, and outputs control signals to the video processor 10 through a serial data line SDL and a serial color line SCL, so that the brightness of the picture is relatively heightened if the external environment of the appliance is bright, while the brightness of the picture is relatively lowered if the external environment is dark.
Such a brightness control prevents eye strain caused by the phenomenon that the human's eye senses the picture as being relatively too dark or too bright when the external environment of the appliance is bright or dark, respectively.
The decoder and D/A converter 13 in the video processor 10 decodes and analyzes the control signals inputted from the microprocessor 12, and quantifies the analyzed control signals through D/A conversion to output control data for controlling the respective circuit blocks of the video processor 10.
The contrast control section 14 controls the amplitude of the input RGB primary color signals in accordance with the contrast control signal outputted from the decoder and D/A converter 13, and the brightness control section 15 controls the brightness of the picture to be displayed by controlling the DC bias voltage level of the amplitude-controlled RGB primary color signals in accordance with the brightness control signal outputted from the decoder and D/A converter 13 to output the brightness-controlled RGB primary color signals to the white point control section 16.
The white point control section 16 controls the respective levels of the RGB primary color signals outputted from the brightness control section 15 in accordance with the color control signal outputted from the decoder and D/A converter 13 to control the color of the entire picture. The RGB primary color signals outputted from the white point control section 16 is inputted to the CRT driving circuit through the output buffer section 17.
By the above-described control operation, the brightness of the picture is increased when the external environment is relatively bright, while the brightness of the picture is decreased when the external environment is relatively dark, thereby reducing the fatigue of the viewer's eye.
Meanwhile, if the blue color is intensified in the external environment, the color temperature of the picture is controlled to be lowered so that the blue color is intensified in the displayed picture, while if the red color is intensified in the external environment, the color temperature of the picture is controlled to be heightened so that the red color is intensified in the displayed picture.
As a result, according to the conventional color control device, the contrast, brightness, and color of the picture to be displayed on the screen are continuously controlled in accordance with the brightness and color of the external environment of the television receiver sensed by the luminance sensor and color sensor, thereby providing the picture optimum to the viewer eye's sensation.
However, according to the conventional color control device, the picture display condition is determined only by detecting the brightness and color of the external environment, but the picture atmosphere which the viewer feels differently in accordance with the environmental temperature of the appliance is not considered. Specifically, if the color temperature of the picture is low and thus the picture atmosphere becomes cold when the environmental temperature is low, the viewer will feel the cold more severely from the displayed picture. Also, if the color temperature of the picture is high and thus the picture atmosphere becomes hot when the environmental temperature is high, the viewer will feel the heat more severely from the displayed picture. The color control operation without considering the environmental temperature may give the viewer an unpleasant feeling or irritate the viewer.